This invention relates generally to paging radio receivers. More specifically, this invention is directed to a paging receiver that is capable of selectively receiving a plurality of sequential tones which may or may not be preceded by a preamble tone.
Paging radio receivers are used to alert a user (a subscriber to a radio paging system). Upon receipt of a page, a user carries out some pre-arranged activity, such as calling his office to receive a telephone message. A paging message for a particular receiver is provided by transmitting from a central facility a sequence of signals, usually tones of selected frequencies in the audio range, on a radio carrier. The particular frequencies transmitted in the sequence constitute the address of a specific paging receiver and are detected by only a specific receiver arranged to detect the particular frequencies in that sequence. When the particular frequencies in that sequence are detected, the paging receiver produces a paging signal (also referred to as a "page") to alert the user that his attention is required. The user can then call a prearranged number, or perform a prearranged duty. Thus, paging receivers provide a useful function for people in many types of occupations and vocations.
Paging receivers now in common use do not take full advantage of the availability of mass production of binary circuits in the form of microcircuits. Thus, they are not as compact and functional as they could be.
Furthermore, some paging receivers utilize a battery saving device that repeatedly turns the receiver on to listen for a paging signal or transmission. Such a receiver requires a preamble (usually a tone) to be transmitted so as to enable the receiver to be active when the sequential paging tones are transmitted. Without a battery saving device, a paging receiver is kept on at all times to listen for its sequence of tones.
Thus, some paging systems operate with a six (6) tone slot format including a preamble and other systems operate with a five (5) tone slot format. The six tone format permits the use of the "battery saving" type paging receiver. At the present time, it is necessary to use a paging receiver compatible with the paging system within which it operates. Thus, it would be desirable to have a paging receiver selectively operable in either format.